Self-consistent particle-in-cell simulations of fundamental and harmonic plasma radio emission mechanisms

Thurgood, Jonathan; Tsiklauri, David

doi:10.1051/0004-6361/201527079

Cited by 48 publications

(75 citation statements)

References 44 publications

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“…In addition, only rather high‐velocity (0.5 c ) and dense (1% to 10% of the background) electron beams have been considered. Recently, Thurgood and Tsiklauri () partially overcame all these limitations by performing 2D3V PIC simulations with lower‐density and slower beams and a larger number of particles per cell. Another approach of the problem has also been developed by Ziebell et al () who performed numerical simulations integrating the full set of weak turbulence equations.…”

Section: Introductionmentioning

confidence: 99%

Electromagnetic Simulations of Solar Radio Emissions

et al. 2019

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Solar radio emissions are electromagnetic waves emitted in the solar wind as a consequence of electron beams accelerated during solar flares or interplanetary shocks such as interplanetary coronal mass ejections. Different physical mechanisms have been suggested to describe their origin. A good understanding of the emission process would enable to infer the kinetic energy transferred from accelerated electrons to radio waves. Even if the electrostatic case has been extensively studied, full electromagnetic simulations were attempted only recently. In this work, we report large-scale 2D3V electromagnetic particle-in-cell simulations that enable to identify the generation of both electrostatic and electromagnetic waves originated by a succession of plasma instabilities. They confirm that an efficient mechanism to generate solar radio emissions close to T 2f , the harmonic of the plasma frequency, is a multistage model based on a succession of nonlinear three-wave interaction processes. Through a parametric study of the electron beam parameters, we show that (i) the global efficiency of the multistep conversion mechanism from the electron beam kinetic energy to the T 2f radio wave is independent of the beam parameters, approximately 10 −5 in all tested configurations, while (ii) the directivity of the electromagnetic radio wave strongly depends on the origin electron beam. Those results represent a step forward toward the use of solar wind radio emissions, observed remotely, as a diagnostic for the properties of the electron beam located at the source of the radio emission, and therefore to eventually better characterize remotely electron acceleration mechanisms in space regions not directly accessible to in situ measurements. Key Points:• We single out the successive steps of the generation mechanisms of solar radio emissions • We quantify the energy transferred from energetic particles to radio waves and show it is independent of energetic particles parameters • We identify the directivity of the radio emissions and show its strong dependence on energetic particles parameters.

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Section: Introductionmentioning

confidence: 99%

Electromagnetic Simulations of Solar Radio Emissions

et al. 2019

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“…The presence of a population of counter propagating Langmuir waves is an essential component in typical models of harmonic solar radio emission whereby their three-wave coalescence produces the emission. Usually, the population of counter-propagating Langmuir waves is thought to be created through electrostatic decay of the forward propagating waves into ion-acoustic waves and backwards propagating waves (such as in the self-consistent emission simulations of, e.g., Thurgood and Tsiklauri 2015). However, in this case we find that a population of counter-propagating Langmuir waves can easily be created in the absence of such three-wave interactions, a population which could then proceed to coalesce and participate in harmonic radio emission.…”

Section: Discussionmentioning

confidence: 99%

Particle-in-cell simulations of the relaxation of electron beams in inhomogeneous solar wind plasmas

Thurgood

Tsiklauri

2016

J. Plasma Phys.

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Previous theoretical considerations of electron beam relaxation in inhomogeneous plasmas have indicated that the effects of the irregular solar wind may account for the poor agreement of homogeneous modelling with the observations. Quasi-linear theory and Hamiltonian models based on Zakharov's equations have indicated that when a level of density fluctuations is above a given threshold, density irregularities act to de-resonate the beam-plasma interaction, restricting Langmuir wave growth on the expense of beam energy. This work presents the first fully kinetic particle-in-cell (PIC) simulations of beam relaxation under the influence of density irregularities. We aim to independently determine the influence of background inhomogeneity on the beam-plasma system, and to test theoretical predictions and alternative models using a fully kinetic treatment. We carry out 1D PIC simulations of a bump-ontail unstable electron beam in the presence of increasing levels of background inhomogeneity using the fully electromagnetic, relativistic EPOCH PIC code. We find that in the case of homogeneous background plasma density, Langmuir wave packets are generated at the resonant condition and then quasi-linear relaxation leads to a dynamic increase of wavenumbers generated. No electron acceleration is seen -unlike in the inhomogeneous experiments, all of which produce high-energy electrons. For the inhomogeneous experiments we also observe the generation of backwards propagating Langmuir waves, which is shown directly to be due to the refraction of the packets off the density gradients. In the case of higher-amplitude density fluctuations, similar features to the weaker cases are found, but also packets can also deviate from the expected dispersion curve in (k, ω)-space due to nonlinearity. Our fully kinetic PIC simulations broadly confirm the findings of quasi-linear theory and the Hamiltonian model based on Zakharov's equations. Strong density fluctuations modify properties of excited Langmuir waves altering their dispersion properties.

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“…To explain this scattered ellipticity values, we analyzed the 2‐D simulation data to check if there are any nonlinear wave phenomena that affect the wave ellipticity. Nonlinear wave‐wave interactions can lead to nonlinear eigenmode/s that is different from the linear dispersion modes [ Rhee et al , ; Thurgood and Tsiklauri , ]. The nonlinear eigenmode could in turn affect the ellipticity value calculated based on minimum variance.…”

Section: Effects Of Superposition Of Waves On Ellipticitymentioning

confidence: 99%

Coherency and ellipticity of electromagnetic ion cyclotron waves: Satellite observations and simulations

Remya

Lee

et al. 2017

JGR Space Physics

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Coherency (C) and ellipticity (ε) of electromagnetic ion cyclotron (EMIC) waves are studied using Cassini data in the Earth's dayside low‐latitude magnetosphere from L = 7 to 10. The results are compared with linear kinetic theory, 1‐D and 2‐D simulations. The EMIC waves are observed to occur in packets with multiple wave cycles. The wave cycles within a wave packet are observed to have the same general propagation angle θkB0 and polarization. In observations and 2‐D simulations, EMIC waves have a mixture of circular and elliptical polarization for θkB0<30°. This scattered ellipticity values are due to the superposition of multiple wave modes. For wave propagation angles 30° <θkB0<60°, the waves are highly elliptical (0.2<|ε|<0.7), where ε is the ratio of minor to major axis of the polarization ellipse. For θkB0>60°, the waves are nearly linearly polarized (|ε|≤0.1). This general trend is in good agreement with linear kinetic theory and 1‐D simulations. Observations indicate right‐hand (RH) wave packets to be interspersed with the left‐hand (LH) wave packets. We show for the first time from linear theory that ion temperature anisotropies can generate RH waves at large propagation angles and for plasma beta βi>0.05. The observed mixture of RH and LH waves in the magnetosphere could be due to this direct generation of RH waves. Observations and simulations show that EMIC waves are coherent with 0.5 < C < 1.0 for θkB0≤50°. Here C is measured as the maximum value of cross‐correlation coefficient between the transverse magnetic field components of the wave.

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Self-consistent particle-in-cell simulations of fundamental and harmonic plasma radio emission mechanisms

Cited by 48 publications

References 44 publications

Electromagnetic Simulations of Solar Radio Emissions

Electromagnetic Simulations of Solar Radio Emissions

Particle-in-cell simulations of the relaxation of electron beams in inhomogeneous solar wind plasmas

Coherency and ellipticity of electromagnetic ion cyclotron waves: Satellite observations and simulations

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